In the course of machining precision parts it is customary to check the part for size by comparing it to a part of nominally ideal or perfect size. One prior art apparatus for accomplishing this comprises a vertical glass tube through which air is caused to flow in varying rates according to the size deviation of a part under inspection. The vertical air column supports an indicator float in a vertical position which is related to part size. Thus, a given float position may be equated to ideal or mean size while positions above and below the given position may be equated to part sizes which are over and under the mean value, respectively.
The columnar display format of the pneumatic size gage is highly favored in view of the graphic character thereof and the ease with which part size may be compared to tolerance limits. However, the pneumatic character of the gaging device described above is disadvantageous from the standpoint of cost, maintenance, and adaptability to expanded data gathering, processing, and display functions. Accordingly, it is desirable to provide an entirely electronic implementation for a gage preferably utilizing the columnar display format and having the characteristics of high accuracy, simplicity of operation, low cost and adaptability to additional display and/or data gathering and processing functions.